Telegraph repeater



April 3, 1951 57:47 ION A DE MOTTE W. GILBO TELEGRAPH REPEATER FiledJan. 27, 1949 SHIT/ON 8 //v l ENTOR 0. W LI/L50 ATTORNEY Patented Apr.3, 1951 TELEGRAPH REPEATER De Motto Whitcomb Gilb to American Teiephon0, Flint, Mich., assignor e and Telegraph Company, a corporation of NewYork Application January 27, 1949, Serial No. 73,110

4 Claims.

This invention relates to telegraph systems and. more particularly to animproved halfduplex direct current telegraph system which includes atelegraph repeater at each terminal in which repeater a separate breakrelay is not required.

By a half-duplex telegraph system, as used herein, is meant a systemwhich is arranged for transmission in only one direction at a time. Thatis to say, if station A at one terminal is transmitting to station E atthe opposite terminal, station E cannot transmit simultaneously tostation A. In such a system it is necessary to provide some meanswhereby a station which is normally receiving may interrupt transmissionfrom the sending station so as to permit the receiving station totransmit toward the sending station. In all half-duplex direct currenttelegraph systems, so far as is known, separatemeans, known generally asa break relay, have been provided in the repeater at each terminal toperform the breaking function in response to a breaking signaltransmitted from the distant station. In the arrangement of the presentinvention, the break relay or any separate element equivalent thereto,is dispensed with.

An object of the present invention is the provision of a half-duplexdirect current telegraph system in which separate means for performingthe break function is not required.

The invention may be understood from the following description when readwith reference to the associated drawing, which taken together, disclosea preferred embodiment of the invention, and in which the single figureof the drawmg shows a half-duplex direct current telegraph in the topWinding system which includes the break feature but has 7 no breakrelay.

In the drawing there is shown at the left, a telegraph repeater station,station A, to which is connected a subscribers loop station, loop A, andat the right of the figure, a telegraph repeater station, station E, towhich is connected a subscribers loop, loop '13.

Loop A extends from repeater station A, to the subscribers premises,whereat are located a telegraph transmitter l and a telegraph receiver2, which may for instance be 'parts of the well knownteletypewritertransmitter and re ceiver instrument. At station A arelocated the repeater polar sending relay 3, and the repeater polarreceiving relay 4. Similarly, a transmitter 5 and receiver 6 are locatedat the subscribers station in loop B, and a polar transmitting relay I,and a polar receiving relay 8 are located at repeater station E.Repeater station A and repeater station B are interconnected bytelegraph channel 9.

When the system is in the marking condition, the armature of receivingrelay 4 at station A is in engagement with its marking contact l4}, andthe armature of sending relay 3 is in ensagement with its markingcontact H. Similar ly, the armature of receiving relay 8, at station E,is in engagement with its marking contact 12, and the armature ofsending relay 1 is in engagement with its marking contact 13. A circuitmay therefore be traced from negative bat tery through marking contactI0 of station A to the apex of relay 3. From this point one branch ofthe circuit extends through the top winding of relay 3 through conductorIt, mag netic receiver 2, and transmitter I, to positive battery. Fromthe apex of relay 3 a second branch of the circuit may be traced throughthe bottom or biasing winding of relay 3, resistance I5 and resistanceHi to ground. From the junction between resistance l5 and It, acondenser I1 is connected to ground. The efiect of the current throughthe top winding of relay 3 for this condition tends to actuate itsarmature to engage its marking contact II. This effect is opposed by theefiect of current flowing through the bottom winding of relay 3, whichis tending to actuate the armature of relay 3 to engage with its spacingcontact 18. The efiect of the current is dominant, however, and thearmature of relay 3 is therefore maintained in engagement with itsmarking contact H.

When the armature of relay 3 is in engagement with its marking contact II, a circuit may ,e traced frompositive battery through marking contactII, to junction it where the circuit branches. The main transmissionpath of the circuit continues through variable resistance 26, to theapex of relay 4, where the circuit again branches. The main transmissionpath continues through the top winding of relay 4, telegraph channel 9,top winding of relay 8, variable resistance 2| and marking contact it,to positive battery. From junction 35 a branch of the circuit extends tospacing contact 34 of relay 8. From junction I 9 a branch of the circuitextends to spacing contact 22 of relay 4. From the apex of relay 4 abranch of the circuit extends through the bottom or biasin winding ofrelay 4 and variable resistance 23 to ground. Variable re sistance 23 isshunted by a series branch consisting of variable resistance 24 andcondenser 25. Since positive battery is connected to each end of themain transmission path, no current flows through the top windings ofrelays 4 and 8 for the marking condition. The efiect of the currentflowing through the bottom or biasing winding of relay 4 for thiscondition maintains the armature of relay 4 in engagement with itsmarking contact Ill. A circuit may be traced from positive batterythrough marking contact 13, variable resistance 2|, bottom or biasingwinding of relay 8 and variable resistance 26, to ground. Variableresistance 26 is shunted by a series branch consisting of variableresistance 21 and condenser 28. The effect of the current flowing in thebottom or biasing, winding of relay 8 for this condition, maintains thearmatureof relay 8 in engagement with its marking contact 12. l

A circuit may be traced from negative battery through marking contact [2to the apex of relay 1. The main transmission path extends throughthe'top winding of relay 1, loop conductor 29, magnetic receiver 6 andtransmitter 5, to positive battery. From the apex of relay 1 a branch ofthis circuit extends through the bottom or biasing winding of relay 1,resistance 30 and resistance 3|, to ground. A condenser 32 is connectedbetween ground and the junction between resistances 30 and 3|. Theeffect of the current flowing in the top winding of relay 1 tends toactuate its armature to engage with its marking contact !3 and thiseffect is dominant over the effect of current flowing in the bottomorbiasing Winding of relay 1 tending to actuate the armature of relay 1to engage with its spacing contact 33, so that the armature of relay 1is maintained in engagement with marking contact l8 for this condition.Since current flows in both loop A and loop B, magnetic receivers 2 and6 are energized for the marking condition.

It will be assumed that the subscriber in loop A wishes to transmit tothe subscriber in loop B. For this purpose, the contacts of theteletypewriter transmitter i, will be actuated so as to alternately openand close the loop. When the loop is open, no current will flow throughthe top winding of relay 3. The armature of relay 3 will therefore beactuated to engage with its spacing contact i8 under the influence ofcurrent in the bottom winding of relay 3. armature of relay 3 engagesits spacing contact 18 negative battery at station A is connected to oneend of the main transmission path, while positive battery remainsconnected to the opposite end. The current through the bottom or biasingwinding of relay 4, will therefore be reversed, and its eiTect will tendto actuate the armature of relay 4 to engage with its spacing contact22. However, current of'considerably larger magnitude will flow throughthe top or line winding of relay 4, and its effect, tending to maintainthe armature of relay 4 in engagement with its marking contact 10, willbe dominant over the eiiect of the current flowing in the biasingwinding, so that the armature of relay 4 will be maintained on itsmarking contact. At station B, however, the current through the top orline winding of relay 8 will be dominant over the eifect of the currentin the lower or biasing wind-- ing and the armature of relay 8 will beactuated to engage with its spacing contact 34. When the armature ofrelay 8 engages with its-spacing contact 34, a circuit may betraced'from positive battery through marking contact l3 of relay 1 andspacing contact 34 of relay 8, to the apex of relay 1. For thiscondition no current will When the 29, through receiver flow through thetop winding of relay 1 since positive battery is connected to each endof subscribers loop B. The polarity of the current through the bottom orbiasing winding of relay "I has now been reversed. Since it formerlytended to actuate the armature of relay 1 to engage with its spacingcontact 33, it will now be effective when no current flows through thetop winding of relay 1 to maintain its armature in engagement with itsmarking contact IS. The spacing signal transmitted over loop conductor 6deenergizes the receiving magnet and this will be effective to actuatethe receiver so as to register a spacing signal. When subscribers loop Ais reclosed, the marking condition described heretofore will bereestablished. Thus marking and spacing communication signal elementsmay be transmitted from loop A to loop B. In a generally correspondingmanner, marking and spacing communication signal elements may betransmitted from loop B to loop A.

When such signals are transmitted from loop B, it should be understoodfrom the foregoing that relay 1 will actuate its armature between itsmarking and spacing contacts I3 and 33. Relay 8 will be unafiected aswas relay 4 and the armature of relay 8 will be maintained in engagementwith its marking contact l2. Relay 4 will respond to the signalsreceived at station A from station B in the same manner as did relay 8at station B for the signals received from station A. The armature ofrelay 4 will be actuated between its marking contact l0 and its spacingcontact 22. Relay 3 will not respond to these signals, however, for thesame reason as described for relay 1, and the receiving device 2 in loopA will register the communication signal.

It will be now assumed that loop B is transmitting communication signalsand loop A wishes to break. To perform this function, a long spacingsignal is transmitted from loop A. In response to this, assuming stationA marking, the armature of relay 3 will be actuated to engage itsspacing contact I8.

There are two conditions now to be considered. If the armature of relayI is on its marking contact [3 at this instant, a spacing signal will bereceived by relay 8 and its armature will engage its spacing contact 34.For this condition no current flows in'loop B because positive batteryis connected to each end of loop B and the loop is closed since amarking signal is being transmitted. Loop B is deenergized. Positivebattery through contacts l3 and 34 will flow through the bottom windingof relay 1, resistance 30 and resistance 3! to ground, and the armatureof relay 1 will be maintained in engagement with its marking contact l3.When loop B is opened to transmit the next spacing signal element, itwill be ineffective since there is no current in loop B to interrupt.Thus, loop B will remain deenergized, informing the operator that loop Awishes to transmit communication signals, If loop B is transmitting aspacing signal, however, at the instant when the armature of relay 3 isactuated to engage its spacing contact IS in response to a break signal,and relay I at station B has responded while relay 8 has not yetresponded, negative battery will be connected to both ends of the maintransmission path at stations A and B. The armature of both relays v4and 8 will be actuated to engage their spacing contacts 22 and 34respectively. Negative battery will be connected to the station side ofloops A and B. Both loops will be openfor the assumedtransmission of aspacing signal from each. Since there will be no current in the topwinding of relay l, current from negative battery through contact 33 andcontact 34 and the bottom winding of relay i will maintain the armatureof relay 1 on spacing contact as while the spacing signal which is beingtransmitted from loop B persists. When loop B is again closed full loopcurrent will flow from negative battery on spacing contact 33, throughthe armature of relay l, through the spacing contact 34 and armature ofrelay 8, through the top winding of relay "l, through conductor 29,through loop B and back to positive battery. When this occurs thearmatures of relays 4 and 8 will he maintained in engagement with theirspacing contacts 22 and 3a. Thi full loop current flowing in the topwinding of reay I is dominant and causes relay '5 to actuate itsarmature to its marking contact l3 and positive battery will bereconnected to both ends of loop B, deenergizing loop B to provide theloreak signal condition.

Variable resistances 2i? and iii are provided to adjust the linecurrent. Variable resistances 23, and 2d and variable condenser 25 areprovided to adjust the current in the biasing winding of relay 4 andvariable resistances 2t and El and variable condenser 28 are provided toperform the same function for relay 8.

It should be obvious that the polarities or the potential sourcesconnected to the marking and spacing contacts of each sending relay ineach repeater and the polarities of the potential sources connected tothe two terminals of each of the loops may be interchanged withoutaffecting the operation of the repeater. There are other obviouschanges. which may be made. wh ch will be readily apparent to thoseskilled in the art, which changes are comprehended by the invention andit is to be understood that the invention is not limited to theparticular embodiment shown and described herein.

What is claimed is:

1. A half-duplex direct current te egraph s stem, a tee raph repeater insaid s stem, a polar transmitt n relay and a polar receivin re a in saidrepeater, a marking contact. a s acin contact and an armature on each ofsaid rela s, a line winding and a biasing winding on each of said relas. said windin s on e ch of said rela s connected to an a ea indi dualto each of said rela s. a conne tion from the anew of s id t ansmittinare ay directl to a fixed end of s id armature of said receiving relay, aconnection from the fixed end of said armature on said transmitting relato said apex on said receiving re ay, and a connection from said spacincontact on said receiving relav di ect y to said fired end of saidarmature on said transmitting relay and said ape? of said rece vinrelay.

2. In a half-du lex direct current telegraph system, a first and asecond tele raph re eater, a, first and a second telegraph 100p circuitconnected to said first and said second repeater respectively, a teleraph channel interconnecting said re eaters, two telegraph relays only,namely a sending relay and a receiving relay, in each of said repeaters,means in said second repeater, responsive to the transmission of a breaksignal communication signals from said second loop circuit while saidbreak signal persists.

3. A half-duplex direct current te egraph svstern, a teegraph repeaterin said system, a telegraph line and telegraph loop connected to saidrepeater, a polar telegraph sending relay in said repeater, a linewinding on said sending relay in series with said loop, a hiasingwinding on said sending relay having one terminal connected to oneterminal of said line winding to form an apex and the opposite terminalconnected through a lumped impedance to ground, a poar receiving relayin said repeater, a line winding on said receiving relay connectedbetween said line and the fixed end of an armature on said send ngrelay, a biasing winding on said receiving relay connected from a pointintermediate said fixed end of said armature on said sending relay andsaid line winding on receiving relay and through a lumped impedance toground, an armature on said receiving relay having a fixed end connectedto said apex on said sending relay and a spacing contact on saidreceiving relay connected directly to a fixed end of said armature onsaid sending relay.

l. A haf-dup1ex direct current telegraph s stem, said s stem comnrisng afirst telegraph station, a first telegr repeater, a second telegraphrepeater, a second telegraph station. a first telegraph loop circuitinterconnecting said first station. and said first repeater, a sin letelegraph channel interconnecting said repeaters, a second te'egranhloop circuit interconnecting said second telegraph repeater an saidsecond te egraph station. a sending a d a receiving polar relay in eachof said repeaters, said repeaters devoid of any other relay, an armatureand a marking and spacing contact on each o said reays, a transmitter ateach of sa d stations for o enin and closing its connected loop. saidsending relays appl ing polar si n ls through its respective marking andspacing contact to said channel in response to said openin s and closins and a break feature in each of said repeaters, said feature comprisingan individual direct connection from said spacing contact of saidreceiving relay to a fixed end of said armature on said sending rela ineach repeater.

DE MOTTE WHITCOMB GILBO.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Num er Name Date 1,303,036 Cummings May 6, 19191,810,198 Bellamy June 16, 1931

